1. Field of the Invention
The present invention generally relates to a technology for composite light dividing devices and an image apparatus applying the same, and more particularly, to a composite light dividing device adapted for dividing light of multiple wavebands.
2. Description of Related Art
An important function of a typical light dividing device is for example dividing a white light to obtain three color lights, i.e., red (R), green (G), blue (B), or multiple color lights of other colors. The mechanism and structure of the light dividing device may vary in accordance with the used apparatus. Conventionally, the R, G, B color lights can be achieved by color filters (CF) of different colors.
In a flat display, a backlight source is often provided with a liquid crystal spatial light modulator and CFs for achieving full color images. Further, image sensors of digital cameras (DC) also demand CFs for cooperating with color variation calculation to present true colors of the original objects. Moreover, some other larger systems, such as a color video recorder and a rear projection TV, adopt a triple-plate type prism set, a dual plate type prism set, or CFs, for cooperating with a collimating light source to display full color images. When the system adopt CFs, because each painted pixel of each CF presents only one of the R, G, B three primary colors, about two third of the incident white light energy is undesirably absorbed, which lowers the optical efficiency, as well as lifespan of the battery. Further, CFs are featured with very complicated fabrication processing, in which each of the primary colors requires at least one semiconductor yellow light processing, thus has a very high production cost.
Further, U.S. Pat. No. 6,867,828, “Light Guide Apparatus, A Backlight Apparatus and a Liquid Crystal Display Apparatus”, and U.S. Pat. No. 7,164,454, “Color Filterless Display Device, Optical Element, and Manufacture”, propose to employ a micro-prism array having a specific angle or a variable structure micro-grating array serving as a light dividing device, for dividing the white light. The divided white light will be far-field diffracted in the space and thus the white light is decomposed into the R, G, B three primary color lights. However, such a light dividing device has a complicated fabricating process, and a complex structure, and therefore is difficult to achieve a satisfactory yield and a lower production cost. Further, the decomposed R, G, B three primary color lights are going to be divergent along the diffraction angles, and thus being further divergent after entering the display panel, which causes parasitic light, or ghosting images. Such a light dividing device is not an ideal one in practical application of the display panel. Further, the above conventional designs are incapable of improving the aperture ratio and polarization efficiency.
As such, optical elements are being continuously developed of the purpose of replacing CFs, and producing three primary color lights perpendicularly incident into the liquid crystal layer and corresponding to the display panel pixels, while maintaining a high optical efficiency.